This invention relates to a device for automatically fixing bus bars onto an insulating board, and more particularly to an apparatus that automatically performs cutting and fixing operations efficiently and without damaging the insulating board.
In a wiring junction box in an automobile, electrical conductors called "bus bars" are fixed onto an insulating board to form an electrical circuit. Heretofore, the bus bars are fixed onto the insulating board as follows:
As shown in FIG. 10, the bus bars are prepared as a bus bar plate (material) BP including a plurality of bus bars B, which are connected through bridges 2. Bridges 2 are cut and removed from the bus bar plate BP by using the punching section of a press, so that only the bus bars B remain. The bus bars B thus remaining are conveyed to a bus bar fixing station. An insulating board 3 has positioning grooves 59 in which the bus bars B are to be set. At the bus bar fixing station, the insulating board 3 is set over the bus bars B, and the bus bars B are fixed onto the insulating board 3 on a press.
In the above-described bus bar fixing operation, the insulating board 3 is manually set over the bus bars B. Accordingly, the bus bar fixing operation is low in work efficiency. In other words, heretofore no device is available that is able to perform the above-described series of manufacturing steps--the bridge cutting and removing step, the insulating board setting step, and the bus bar fixing step. Hence, there has been a strong demand for a device for automatically fixing bus bars onto an insulating board.
In order to set the insulating board 3 over the bus bars B, it is necessary to hold the insulating board 3 once. In this connection, a suction device may be employed for suctioning and retaining the insulating board, or the insulating board may be clamped with a plurality of cylinders. However, those methods are disadvantageous in that the insulating board is liable to be bent and deformed, which may make it impossible to fix the bus bars onto the insulating board. The insulating board is a thin plate of resin, and therefore it should be lifted and held with great care.
In an alternative arrangement, as shown in FIG. 16, the bus bars are similarly prepared as a bus bar plate (material) BP. The bus bars shown in FIG. 16 are so-called "after-fixing bus bars." The after-fixing bus bars are divided into a first-fixing group of bus bars BP1, which are firstly fixed onto the insulating board (to form a main circuit for instance), and an after-fixing group of bus bars BP2, which are coupled through bridges to the first-fixing group of bus bars (to form an auxiliary circuit for instance). The reason that the bus bars are divided into two groups and fixed on the insulating board separately in this arrangement is as follows:
In general, bus bars are arranged in a limited area on the insulating board to form electrical circuits; that is, it is necessary for the bus bars to use a minimum area on the insulating board. The bus bars are provided by blanking such that they form a predetermined pattern and have tabs at predetermined positions that are bent. Hence, it is necessary to provide a certain space between adjacent bus bars that is large enough to provide the tabs. In order to form electrical circuits with the bus bars of this type, it is necessary to use a large insulating board.
Among the bus bars, those that suffer from interference are separated so that they are fixed onto the insulating board at a different time from the time when the remaining are bus bars fixed. That is, the bus bars are not provided as one unit, and instead, they are divided into a plurality of groups that are fixed on the insulating board separately. This is the reason why the after-fixing bus bars have been proposed.
The after-fixing bus bars are fixed on the insulating board as follows: First, the bridges 2 are cut and removed from the bus bar plate BP with the punching section of a press, so that only bus bars B remain. The bus bars B thus remaining are conveyed to the bus bar fixing station. The insulating board 3 has positioning grooves 59 in which the bus bars B are to be set. At the bus bar fixing station, the insulating board is set over the bus bars B, and the bus bars B are fixed onto the insulating board on the press.
In the above-described punching operation, the bus bars of the bus bar plate are divided into the first-fixing group of bus bars and the after-fixing group of bus bars. As was described above, the after-fixing group of bus bars are provided outside of the first-fixing group of bus bars. Therefore, particular operations must be carried out. That is, it is necessary to rearrange the after-fixing group of bus bars and to take the bus bars thus rearranged in the first-fixing group of bus bars. However, heretofore, no device for automatically performing those operations is available, and the operations are carried out manually. In addition, the operator must set the insulating board over the bus bars thus rearranged. Hence, the conventional bus bar fixing operation is rather troublesome and suffers from poor work efficiency. This difficulty accompanying the after-fixing bus bars has been pointed out in the art; however, no suitable counter-measure has been proposed.